1. Field of the Invention
Embodiments of the present invention relate to the manufacturing of electronic components on wafers used as a substrate and, more specifically, to so-called single face products, that is, having their components supported by a single surface of the wafer.
Embodiments of the present invention more specifically apply to the manufacturing of passive components on glass substrates.
2. Discussion of the Related Art
The search for component miniaturization goes along with a need to reduce the thickness of the wafers or substrates supporting these components. The small thickness desired for the final components is, however, incompatible with the stress undergone by the wafers during manufacturing, and the final thickness of the individual substrate of the component is accordingly achieved at the end of the process.
An example is the forming of passive components on glass substrates wherein the components are formed on one surface, arbitrarily called the front surface, of a relatively thick glass wafer (more than 500 micrometers). Then, the wafer is grinded on its rear surface deprived of any component to reach the final thickness desired for individual substrates (200 micrometers, or even less).
At the end of the thickness reduction, the wafer considerably loses its mechanical strength. Now, the handlings required in subsequent steps, among others of cleaning and washing, resulting in risks of cracks or breaks of the structures of the component formed at the front surface.
It should be noted that this risk of breakage of the structure is already present in the rectification step, due to the irregular bearing of the front surface which supports the components. The unevenness of the front surface typically is on the order of some twenty micrometers (thickness variation of the front surface at the end of the component manufacturing). The irregular bearing resulting therefrom, associated with the pressure applied by the grinding wheel on the rear surface, causes breakage risks, especially at the end of the rectification step when the wafer becomes thinner and thinner and this thickness difference is no longer negligible as compared with the general wafer thickness. This is especially why the final thicknesses of the wafers, rectified at their rear surface after manufacturing of the components, are generally no smaller than 200 μm.
Another disadvantage is linked to a deformation of the wafer which becomes slightly bulged (warp) when it is thin. This deformation especially results from the presence of the components on a single surface. This curvature may impede the wafers from being housed in batch processing baskets. As an example, with a deflection reaching 3.2 mm, the introduction of the thin wafers in usual handling baskets is no longer possible.